Calling device



Patented Apr. 7, 1925.

UNITED 1 STATE-Sg- PATENT OFFICE.

FRED L. IBAER, or LA eannen, IL INcIs, ess'Ie-N'on ro aU'roM 'rIoELECTRIC corarANY, or CHICAGO, ILLINoIs, a conronn'rron or ILLINOIS.

CALLING nnvrcn.

$i1bstitute for abandoned application Serial No. 525,931, fi1ed December30, 1921.

" V filed. May 13, 1%22.

To all: whom it may concern.

Be it known thatI, FRED L.- BAER, a citizen of the United States ofAmerica, and a resident of La Grange, Cook County, and State ofIllinois, have invented certain new and useful Improvements in CallingDevices, of which the following is a specification.

The present invention relates in general to calling devices or impulsesenders for automatic telephone systems, and the object of the inventionis to provide a novel and improved number plate which renders callingdevices of the above character better adapted for use in large systems.

The invention is illustrated in the accompanying drawings, in which Fig.1 shows a front view of a calling device equipped with the improvednumber plate, while Figs. 2 and 3 show the number plate of Fig. 1 and amodification thereof, respectively.

' In mechanical construction the calling de vice shown may be or" thetype shown and described in the book, Automatic Telephony, by Smith andCampbell, second edition, pages 40 and ll. As is well known, a callingdevice of this kind isprovided with a finger hole dial which is operablein accord ance with the digits in a called telephone number to transmitcorresponding series of impulses over the line to the exchange, in

order to operate a plurality of serially re- 7 lated automatic switchesreestablish the desired connection.

In the beginning, such calling devices had the finger holes designatedby numerals only, and the telephone numbers as listed in the directorywere composed solely of numerals, as for example, No. 4567. Later on,and especially in large systems, it became the practice to prefix one ormore letters to the digits of the directory numbers, forming so calledcomposite numbers such as A 4567. At the same time, of course, letterdesignations were added to the calling device number plates and eachfinger hole was marked with a numeral and also with a letter. The

use of one or more letters in place of the corresponding numerals madeit easier for the subscribers to remember the telephone numbers.

A further modification or improvement has been brought about by theintroduction This application; Serial Ito. 550,633.

of automatic systems in very large cities, wnerethe telephone populationis so largeas to require the use of as many as sevendigits in thetelephone numbers. Such large systems are made up of a large number 01.different ofiices orexchanges, and ithas been. proposed to use the firstthree letters of the exchange name in place of the first threed'igits'ot each telephone number. The compositenumbers thus formed areusually sug: gestive of the exchanges to which the subscribers areconnected and consequently are easily remembered. In order to preventconfusion resulting from the subscribers calling too-many letters, thefirst three letters of each exchange name, which are the only ones whichhave to be dialled, are printed in heavy type, as for example, MONroe3200, or KIIidare 9467.

The spelling of the exchange names, or rather of parts of them, requiresthe use of allletters of the alphabet except- Q, and' Z, which are notusually found in the names of exchanges. According to known practice,these letters are arranged on the number plate with the letters ABCassociated with the digit 2, letters DEF associated with the digit 3,letters GIII associated with the digit 4:, and so on, which bringsletters WXY in the'finger hole allotted to the digit 9, it beingunderstood that letters Q and Z are omitted.

The above described arrangement for a calling device has been consideredsatisfactory, and it has the advantage that there is only one vowelineach finger hole, which makes it possible to spell a maximum num ber ofexchange names. Another point, usually considered an advantage, is thatnone "of the three letter combinations, as ABC,

spell an ordinary word. I have discovered however, a great disadvantage,one which is inherent in the numbering scheme employed, and which isentirely obviated by the present invention. The difficulty arises fromthe fact that the letter I is in the same finger hole with the digit 4,while the letter O is in the same hole with the digit 6. Letters I and Oare very similartothe digits 1 and 0 (Zero), respectively, and asubscriber in calling I, for example, is liable to call the digit 1instead, which causes only one impulse to be transmitted instead of iand results in a wrong number. The misthe one shown in Fig. 3, in whicha single takes thus made are natural, and'constitute a serious defect inthe system. 7

A new method of numbering .or assigning the letters has been devised,therefore, which is systematic, which retains all the good features ofthe old plan, and which at the same time completely eliminates thedefects pointed out 'above. According to the new scheme, and referringespecially to Fig.2 of the drawings, I begin by assigning the letter Ato the finger hole'occupied by the digit 2, and assign the succeedingletters B, C, etc., to the next higher digits 3, 4, etc., going aroundthe number plate in a counterclockwise direction until the letter I isreached. This letter is not assigned to the digit 0 (zero), but isassigned instead to the digit 1, and the numbering then continues asbefore, letter J being assigned to the digit 2, letter K to the digit 3,etc., until the letter O is reached. At this point enough digits areskipped to bring the letter O in the same finger hole with the digit 0(zero), whereupon the numbering continues as before until the lettersare exhausted, it being noted, however, that letters Q and Z areomitted. Thisbrings the last letter Y in the finger hole occupied bythedigit 9. Of course if it is desired one or both of the letters Q, andZ could be included, as there is space available in the last and firstfinger holes.

It will be seen that according to the foregoing plan the letters areassigned to the finger holes in regular order, the circuit-of the dialbeing repeated until all the required letters are located, with theexception that when letters I and O are reached enough finger holes arepassed by to place these letters in the finger holes occupied by digits1 and 0 (Zero), respectively, which are the ones they most nearlyresemble. By this procedure all trouble due to errors of the subscribersin calling the letters or digits particularly mentioned is avoided, foreach of these letters is in the same finger hole with the correspondingdigit and it makes no difference therefore whether the subscriber callsthe letter or the digit, as the same number of impulses will betransmitted in either case.

The number plate marked according to the above method is perhaps thepreferred form, and is especially so in case the letters are printed inthe directory in one color and the numerals in another color, as maybedone, or in case the type used is substantially different in the caseof the letters and numerals. It may happen, however, that only one coloris used, and that thestyle of the type is such that letters I and O are.nearly or exactly identical with numerals 1 and 0 (Zero), respectively.

In this case the number plate may be like character is used to designatethe letter I and the numeral 1, and a single character fordesignating'the' letter O and the numeral 0 (zero). Y I r What I claimis:

1. A calling device for automatic telephone systems having a rotatablefinger hole dial, impulse sending mechanism variably controlled by thedial in accordance with the finger hole used,digit designations for thefinger holes, and letter designations for the finger holes-also, thesaid letter designations being assigned to the holes according to amethod which brings letters 0 and I in the same holes as the digits 0and 1, respectively, therebyrendering it immaterial so far as the numberof. impulses transmitted is concerned whether the subscriber calls thesaid letters or the said digits. e

2. As an article of manufacture, a number plate for automatic callingdevices, said number plate having characters representing digits andother characters representing letters, each letter being associated witha digit, and the letters 0 and I being associated with the digits 0 and1, respectively.

8. As an article of manufacture, a number plate for automatic callingdevices, said number plate having characters representing the ten digits1 to 0, inclusive, and all the letters of the alphabet except theletters Q and Z, there being one or more letters associated with eachdigit, and the letters 0 and I being associated with the digits 0 and 1,respectively.

41. As an article of manufacture, a number plate for automatic callingdevices, said number plate having a pluralityof characters representingdigits, a second plurality of characters representing letters, and athird plurality of characters which represent both letters and digits.

5. As an article of manufacture, a calling device number plate having aplurality of number positions corresponding to the finger holes of acalling device dial, said positions being occupied by characterscorresponding to the digits 1 to O, inclusive, the positions which areoccupied by the digits 1 and 0 being occupied also by charactersrepresenting the letters I and 0, respectively, and each of the otherpositions being ioccupied also by characters representing one or more ofthe remaining letters.

7 6. The method of assigning letters of the alphabet to a number platefor a calling device, which consists in allotting the letter A to thedigit 2 and in allotting succeeding letters to the next higher digits inorder until the letter I is reached, which is allotted to the digit 1,in allotting the letters following the letter I to the digits follow- 5in regular order beginning with the digit 1.

7. The method of assigning letters of the alphabet t0 the numberedfinger holes of a calling device, Which consists in assigning theletters to the several finger holes 10 in regular order, the processbeing repeated as often as is necessary to locate all the lettersrequired, and Which consists further in passing by sufficient fingerholes when the letters I and O are reached to locate these letters inthe finger holes occupied by the digits 1 and 0, respectively.

In Witness whereof, I hereunto subscribe my name this 9th day of May, A.'D., 1922.

FRED L. BAER.

